SEATTLE (AP) - Longshoremen began picketing Tuesday at the site of Seattle's $3.1 billion tunnel project after claiming four jobs along the waterfront have been improperly given to workers with other unions.

A couple dozen members of the International Longshore and Warehouse Union blocked access to the waterfront area where the four workers would be operating. ILWU Local 19 President Cameron Williams said the mobilization will continue until there is movement toward giving the work to the longshoremen.

Boring at the tunnel project began just a few weeks ago, as the world's largest tunneling machine started digging a pathway that will ultimately carry vehicles under downtown. The longshoremen are upset about four jobs that involve loading excavated dirt onto a barge.

Williams said the ILWU members are upset because they believe a contract signed earlier this year gives them the barge-loading jobs. ILWU workers view the waterfront positions as their territory.

Chris Dixon, project manager for contractor Seattle Tunnel Partners, said the contract signed in April was done under duress because the ILWU was refusing to offload the boring machine unless officials agreed to provide them the four jobs now in dispute. An arbitrator ruled last month that the jobs should go to building trades workers under a larger project labor agreement, Dixon said.

Officials aren't planning to begin barge work for about two more weeks, but Dixon said there is some work that needs to be done along the waterfront over the coming days. Dixon said he's not sure what the next steps will be.

"We don't want to escalate the issue," Dixon said. "We're just kind of seeing how things transpire over the next day or two, instead of having some kind of immediate reaction to the situation that would worsen the situation."

The tunnel boring project is expected to take about 14 months to make a nearly 2-mile journey, with the machine surfacing near south Lake Union. Vehicles are expected to begin using the tunnel by late 2015, and the removal of the viaduct will be part of a larger project to renovate the Seattle waterfront.